U.S. patent number 7,744,348 [Application Number 11/763,610] was granted by the patent office on 2010-06-29 for method of producing a hot gas component of a turbomachine including an embedded channel.
This patent grant is currently assigned to ALSTOM Technology Ltd.. Invention is credited to Cyrille Bezencon, Bernd Fehrmann, Matthias Hoebel, Maxim Konter, Wilfried Kurz, Jean-Daniel Wagniere.
United States Patent |
7,744,348 |
Bezencon , et al. |
June 29, 2010 |
Method of producing a hot gas component of a turbomachine including
an embedded channel
Abstract
A component, especially a hot gas component of a turbomachine,
has at least one passage (7, 7'), especially a cooling passage,
which is embedded in an outer wall (5) of the component (1) of the
turbomachine and basically extends parallel to the surface (6) of
the component (1). The component (1) has a basic body (8) and at
least one coating (9) which is applied to the basic body on the
outside, and the passage (7, 7') on one hand is formed by a cavity
which is formed in the basic body (8), and on the other hand is
closed off towards the surface (6) of the component (1) by the
coating (9).
Inventors: |
Bezencon; Cyrille (Chermignon,
CH), Fehrmann; Bernd (Baden, CH), Hoebel;
Matthias (Windisch, CH), Konter; Maxim (Klingnau,
CH), Kurz; Wilfried (La Conversion s. Lutry,
CH), Wagniere; Jean-Daniel (Boussens, CH) |
Assignee: |
ALSTOM Technology Ltd. (Baden,
CH)
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Family
ID: |
34974357 |
Appl.
No.: |
11/763,610 |
Filed: |
June 15, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070253817 A1 |
Nov 1, 2007 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/EP2005/056979 |
Dec 20, 2005 |
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Foreign Application Priority Data
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Dec 24, 2004 [CH] |
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02147/04 |
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Current U.S.
Class: |
416/97R;
416/241R |
Current CPC
Class: |
C30B
13/24 (20130101); F01D 5/187 (20130101); C30B
29/52 (20130101); B23P 15/04 (20130101); B23P
15/02 (20130101) |
Current International
Class: |
F01D
5/18 (20060101) |
Field of
Search: |
;416/236R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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931017 |
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Jul 1955 |
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DE |
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3706260 |
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Sep 1988 |
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DE |
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0113883 |
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Jul 1984 |
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EP |
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1001055 |
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May 2000 |
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EP |
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1295970 |
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Mar 2003 |
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EP |
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1462611 |
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Sep 2004 |
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EP |
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1462613 |
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Sep 2004 |
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EP |
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791751 |
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Dec 1954 |
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GB |
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WO97/35678 |
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Oct 1997 |
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WO |
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WO2006/069941 |
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Jul 2006 |
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WO |
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Other References
Search Report for Swiss Patent App. No. 2147/04 (Apr. 19, 2005).
cited by other .
International Search Report for PCT Patent App. No.
PCT/EP2005/056979 (Mar. 9, 2006). cited by other.
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Primary Examiner: Edgar; Richard
Attorney, Agent or Firm: Cermak Nakajima LLP Cermak; Adam
J.
Parent Case Text
This application is a Continuation of, and claims priority under 35
U.S.C. .sctn.120 to, International application no.
PCT/EP2005/056979, filed 20 Dec. 2005, and claims priority
therethrough under 35 U.S.C. .sctn.119 to Swiss application no.
02147/04, filed 24 Dec. 2004, the entireties of both of which are
incorporated by reference herein.
Claims
What is claimed is:
1. A method for producing a hot gas component of a turbomachine,
the component having at least one passage embedded in an outer wall
of the component, the method comprising: forming at least one
passage-like cavity in a basic body of the component; covering the
at least one passage-like cavity by applying a coating material to
the basic body; locally surface melting the basic body at least on
two sides of the cavity simultaneous with said applying and with
melting the coating material at least in the region of the
cavities, wherein the coating material, a process temperature, and
the width of the cavity are matched to each other so that the
molten coating material does not penetrate into the cavity on
account of surface tension; and cooling and hardening the molten
coating material so that the coating material is epitaxially built
up on the basic body, achieving a metallurgical connection to the
basic body on the two sides of the cavity.
2. The method as claimed in claim 1, wherein said simultaneous
melting of the basic body and said applying of the coating material
comprises a process selected from the group consisting of plasma
spraying, electron beam evaporation, lasering, and combinations
thereof.
3. The method as claimed in claim 2, further comprising: feeding
the coating material in the form of powder or wire.
4. The method as claimed in claim 2, wherein lasering comprises an
epitaxial laser metal forming process.
5. The method as claimed in claim 1, wherein forming at least one
passage-like cavity comprises a process selected from the group
consisting of precision investment casting, mechanically forming,
electrochemically forming, photochemically forming, laser forming,
and combinations thereof.
6. The method as claimed in claim 1, wherein: a first phase of the
hardening of the coating material is of the .gamma.-type, or in the
coating, a transition from the monocrystal structure to the
equiaxial structure is avoided, or in the coating, the formation of
new crystallization germs is avoided, or combinations thereof.
7. The method as claimed in claim 1, further comprising: smoothing
the surface of the coating after said cooling and hardening by
laser melting.
8. The method as claimed in claim 1, further comprising: heating
the basic body before and/or during said coating, to reduce
stresses which occur by the hardening and/or cooling of the
coating.
9. The method as claimed in claim 1, wherein applying the coating
comprises applying so that the coating contains a monocrystalline
structure and/or is epitaxially connected to the basic body.
10. The method as claimed in claim 1, further comprising:
additionally melting the coating material so that a monocrystal
structure of the basic body is reproduced in the coating and/or a
polycrystalline structure of the coating is transformed into a
monocrystal structure.
11. The method as claimed in claim 1, further comprising:
processing the coating after said cooling and hardening so that the
coating contains a monocrystalline structure and/or is epitaxially
connected to the basic body.
Description
BACKGROUND
1. Field of Endeavor
The present invention relates to a component, especially a hot gas
component of a turbomachine, with at least one passage which is
embedded in an outer wall of the component and basically extends
parallel to and close to the surface of the component, which
passage is especially to serve for intake of a cooling medium.
Furthermore, the invention relates to a method for producing at
least one such passage in a component.
2. Brief Description of the Related Art
Modern turbomachines, like, for example, gas turbines, are exposed
to high loads during operation. They are often operated with hot
gases at more than 800.degree. C., and at the same time are
subjected to high mechanical loads. The increase of turbine output
capacity during the last decades is fundamentally based on two
improvements. On one hand, continuously new efficient materials
were developed, like, for example, monocrystal alloys, as a result
of which the load capacity of the components which lie in the flow
cross section of the hot gases could be increased, and on the other
hand, cooling systems and temperature protective coatings, which
were improved time and again, were developed, which resulted in an
increase of the turbine inlet temperatures, and, as a result, an
increase of the turbine output. Monocrystal alloys, like, for
example, CMSX2, CMSX4, or MK4, have especially led to an
appreciable reduction of the temperature sensitivity, and, as a
result, to appreciably improved mechanical properties at high
temperatures. Since the output capacity of gas turbines is directly
coupled with the inlet temperature of the hot gases, for years a
continuous increase of the hot gas temperature has been noted, so
that especially in the first turbine stages gas temperatures are
already achieved which exceed the melting temperatures of the
alloys which are used there. In order to prevent damage of the hot
gas components or the alloys which are used, as the case may be,
complex internal cooling systems were developed, which cool the
components which lie in the flow cross section in such a way that
these lie below a critical temperature limit at which the
components would be damaged. In this case, it is common to all
cooling systems that a compromise has to be made between the
desired cooling effect, the amount of cooling air which is
available, and the costs.
The cooling air which is required for cooling is generally
delivered from a compressor and, by means of an internal cooling
system, is distributed to the components which are to be
cooled.
As a rule, different cooling methods, like, for example, such
methods which are based on a convective heat transfer, are combined
with a film cooling or transpiration cooling. In this case, the
components have internal cooling passages, for example, which
extend in serpentine-like fashion and which interact in a
communicating manner with a multiplicity of discharge openings on a
surface of the component, as a result of which a film cooling or
transpiration cooling is created. An especially effective cooling
is achieved in this case, if the wall which is to be cooled has a
wall thickness which is as small as possible (EP 0 964 981).
Calculations have proved that in a development of a cooling method
of a hot gas component to the effect that a system of cooling
passages which is close to the surface is created, which cooling
passages communicate at least by their one end with the internal
cooling medium passages which pass through the inside of the blade
mostly in serpentine form, while at least one other end is
connected to cooling paths which lead to the surface and effect a
film cooling or transpiration cooling there, lead to an increase of
the turbine inlet temperature by 50K to 125K, and lead to a
significant enhancement of the machine output as a result of it,
without additional consumption of cooling air.
Since, however, as a result of the cooling of the components,
especially of the turbine blades, the overall efficiency of the
power plant decreases, a compromise also has to be found here
between turbine output and turbine cooling.
Another efficient, convective cooling system is effected by means
of coolable wall structures, as it is proposed, for example, in EP
1 462 611, EP 1 462 612, and EP 1 462 613. In this case, the walls
of the hot gas components are equipped with a network of cooling
passages. In the interests of effective cooling, it is advantageous
to construct these walls very thinly and to lay out the cooling
passages close to the thermally stressed surface. In this way, an
efficient cooling can be provided. However, such internal cooling
passages are exceptionally complicated to produce in the
manufacturing process and, therefore, are disproportionately
expensive.
To alleviate this disadvantage, a method for producing or repairing
cooling passages, which are close to the surface, in a hot gas
component of the gas turbine has become known, which is basically
based on a profile being applied to a basic body of this component,
which profile corresponds to the later structure of the cooling
passages. This can be carried out either in the way by a thermally
stable filling material in a corresponding structure being applied
to the surface of the basic body, or by this structure first being
mechanically machined from out of the surface of the basic body and
the cavities which result from it then being filled with the
thermally stable filling material. In a subsequent step, a coating
material is applied by means of a coating method, at least in the
region of the cooling structure. The cooling passages are opened by
means of subsequent removal of the filling material.
This proposal which forms a generic type is disclosed in EP 1 065
026 and also in later publications, like EP 1 462 611 and EP 1 462
612.
By means of these solutions, it will be possible on one hand to
create a cooling passage network in a component of a turbomachine,
which on one hand brings about an efficient cooling of the
component on account of its position which is arranged just beneath
the surface of the outer wall, and which on the other hand can
dispense with costly casting molds and results in lower scrap
rates. The cooling passages, which are embedded in the outer wall
of the component, can generally also be combined with other cooling
strategies, like, for example, the transpiration cooling which is
described above, as a result of which a high flexibility and a
broadened application spectrum can be achieved.
In this method, however, the relatively high manufacturing cost is
still disadvantageous, especially the regular requirement of an
aftertreatment for the subsequent removal of the filling
material.
SUMMARY
One of numerous aspect of the present invention is based on making
available a component of a turbomachine of the aforementioned type,
which especially has an enhanced cooling system with greatly
reduced manufacturing cost. Furthermore, another aspect of the
present invention is based on making available a method for
producing at least one passage which is embedded in an outer wall
of such a component.
Another aspect of the present invention is based first producing in
a first step the structure of the cooling medium passages on the
surface of the basic body in a component of a turbomachine of the
aforementioned type, and, in a further step, applying a coating
material while directly bridging the cooling medium passages which
are produced, without these being masked with a filling
material.
According to principles of the present invention, it is possible,
therefore, to create a number of cooling passages in a component of
a turbomachine which on one hand are simple to produce, and on the
other hand bring about efficient cooling of the component on
account of their position which is arranged just below the surface
of the outer wall, wherein a costly aftertreatment of the component
for the purpose of removing filling material and for opening the
cooling medium passages which are produced, can be omitted.
Production effort, and, as a result, production costs, can also be
appreciably reduced. The cavities which are introduced in the basic
body can be fully automatically produced or applied, as the case
may be, just as the coating, as a result of which an especially
high quality, and, as a result, a high service life, ensue.
The cooling passages, which are embedded in the outer wall of the
component, can generally also be combined with other cooling
strategies, like, for example, transpiration cooling which is
described above, as result of which an especially high flexibility
and a broadened application spectrum can be achieved.
The basic body expediently has an equidirectional grain structure
and/or monocrystal structure. Monocrystal structures are spoken of
when the building blocks of the crystal, consequently the ions,
atoms, or molecules, form a unitary, homogenous crystal lattice. By
means of such a monocrystal, a slipping of the grains along the
grain boundaries, for example as a result of the centrifugal forces
which prevail in the turbine, is avoided, since in monocrystals
there is only just one single grain which at the same time is the
crystal.
In a further advantageous embodiment of the invention, at least one
passage communicates with at least one discharge opening which
leads to the surface of the component. As a result of this, the
especially effective cooling system which extends closely beneath
the surface is combined with a known film cooling, which by
permanent discharge of cooling air through the discharge openings
creates a cooling medium film which is distributed over the surface
of the component. In this case, it concerns a so-called open
cooling system, in which permanent cooling medium, as a rule air,
from a cooling medium source of relatively high pressure, for
example which is branched from the compressor of a gas turbine
plant, is directed into the component which is to be cooled through
its internal cooling passages up to the discharge openings in the
outer wall.
In a further advantageous embodiment, a passage longitudinal axis
is at a distance of less than 3 mm from the surface of the
component. As a result of this, a direct and quick transfer of the
cooling action onto the surface is possible, as a result of which
an especially high cooling effect can be achieved. Furthermore, it
is conceivable in this case that a plurality of passages forms a
communicating passage network and so bring about a uniform, areal
cooling of the surface of the component. By means of different
cross sections inside the cooling passage network, furthermore, the
accurate distribution of the cooling air in the component can be
influenced, so that, for example, regions which are to be cooled
more intensely are equipped with cooling passages of larger cross
section, whereas regions which are to be cooled less intensely have
cooling passages with smaller cross section.
A width of the cavity, at least in the region of a surface, is
expediently less than 1 mm. The width is preferably even only 0.2
mm, as a result of which bridging of the cavity width by the
applied coating is simplified. In the case of a small cavity width,
too great a penetration of the applied coating into the cavity is
also avoided, since the two edges or the two cavity walls, as the
case may be, have a large surface in comparison to the amount of
coating which has penetrated, and, as a result, bring about a quick
hardening of the coating. The small width of the cavity,
furthermore, has the advantage that in comparison to cavities with
larger width, a close-meshed network of cooling passages can be
extended on the surface of the component or of a turbine blade
respectively, and, as a result, a more uniform cooling performance
or individually better adaptable cooling performance, as the case
may be, can be achieved.
Further important features and advantages of the turbomachine
according to the invention result from the drawings, and from the
associated description of the figures, with reference to the
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred exemplary embodiments of the invention are shown in the
drawings and explained in detail in the subsequent description,
wherein like designations refer to like or similar or functionally
similar components.
In the drawing, schematically in each case:
FIG. 1 shows a component of a turbomachine according to the
invention, with passages which are made partially visible and
embedded in the outer wall of the component,
FIG. 2 shows a cross section through the component along a cutting
plane II-II,
FIG. 3 shows a detailed view of cooling passages which are embedded
in the outer wall of the component,
FIG. 4 shows a much enlarged detail of a cross section in the
region of the coating which closes off the passage,
FIG. 5 shows a view as in FIG. 4, however with a previously heated
basic body, and
FIG. 6 shows a view as in FIG. 3, of another embodiment.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
According to FIG. 1, a component 1 of a turbomachine, which apart
from that is not shown, has a region 2 which during operation of
the turbomachine is flow-washed by hot gases. In the case of the
component 1, as exemplarily shown in FIG. 1, it can be a blade 3,
stator blade or rotor blade of a gas turbine. At its seated end,
the blade 3 leads into a blade root 4, by which the blade is
fastened, for example, to a stator or a rotor. In order to increase
the output capacity of the turbine, turbine inlet temperatures
which are as high as possible are desired. High turbine inlet
temperatures, however, disadvantageously affect the service life of
the components 1 which are exposed to hot gas as long as these are
not adequately protected. For protection of the components 1
against the high temperatures of the hot gases, two different
methods are principally adopted. On one hand, it is attempted to
positively influence the temperature resistance of the components 1
which are in direct contact with the hot gases, by a corresponding
material selection, like, for example, by the use of nickel-based
alloys and/or thermal protection layers, and on the other hand, the
components 1 are actively cooled.
A good example, for the progress in material science, is so-called
monocrystal alloys, like, for example, CMSX2, CMSX4, or MK4, which
are frequently used in modern machine construction. Crystals, the
building blocks of which form a unitary, homogenous crystal
lattice, are referred to as monocrystals.
In addition to the material selection which was mentioned, the
blade 3, furthermore, can be protected against damage by the hot
gases by cooling.
According to FIG. 2, for this purpose the blade 3 has passages 7,
7', especially cooling passages, which are embedded at least in one
region of an outer wall 5 and which basically extend parallel to
the surface 6 of the component 1 or the blade 3, as the case may
be. The component 1 has a basic body 8, which, for example, has a
equidirectional graining and at least one coating 9, for example a
connecting layer, which is applied to the basic body 8 on the outer
side. The passage 7, 7' in this case is formed on one hand by a
cavity which is introduced in the basic body 8, and on the other
hand is closed off towards the surface 6 of the component 1 by the
coating 9. Furthermore, it can be provided that the coating 9 on
the outside supports a thermal protection layer 10. The coating 9
in this case, for example, can be a metal coating which protects
the basic body 8 against hot temperature oxidation and temperature
corrosion. In this case, the coating 9 can include the same
material as the basic body 8 and/or, for example, can be a MCRALY
alloy, wherein M stands for nickel, cobalt, iron, or a combination
of these elements. The preferably metal coating 9 in this case can
have a layer thickness of 100 .mu.m to 600 .mu.m. In addition to
the protection function, the coating 9 fulfills a further function,
specifically the provision of an adhesion layer for the
temperature/thermal protection layer 10 which is arranged on the
coating 9 on the outside. The thermal protection layer 10 in this
case can be formed from a ceramic material, like, for example,
ZrO.sub.2, and on account of its insulating action reduces the
thermal stress for the components which lie beneath it. The thermal
protection layer 10 can be applied, for example, by a plasma spray
process or an electron beam evaporation process.
FIG. 3 shows a detailed cross section in the region of the surface
6 of the component 1 or surface of the blade 3, as the case may be,
wherein two passages 7 and 7' are exemplarily shown, which differ
in their cross section. The cooling passages 7, 7' in this case are
embedded in the basic body 8 and have an opening towards the
initially uncoated surface of the basic body 8. As shown in FIG. 3,
the openings of the passages 7 and 7' are bridged and closed off by
the coating 9 which is arranged in the opening region in each case.
In this case, the coating 9, as shown in FIG. 3, can only be
arranged in the region of the openings of the passages 7, 7', or
they can cover the basic body 8 along its entire surface, as shown
in FIG. 6. It is also conceivable that at least one passage 7, 7'
communicates with at least one discharge opening, which is not
shown, which leads to the surface of the component 1 and as a
result creates a film cooling along the surface 6.
In order to fully develop the cooling action of the passages 7, 7',
these have to be integrated into a cooling circuit of the
turbomachine, so that a through-flow of cooling medium through the
passages 7, 7' can be achieved. It is also conceivable that a
plurality of passages 7, 7' form a communicating passage network,
which is shown according to FIG. 3 by a connecting passage 11 which
is shown by discontinuous lines. Furthermore, it is necessary for
an effective cooling of the blade 3 or the component 1, as the case
may be, that the passages 7, 7' lie as close as possible to the
surface 6 of the component 1. Therefore, a passage longitudinal
axis 12, which according to FIG. 3 basically extends orthogonally
to the illustration plane, is preferably at a distance of less than
3 mm from the surface 6 of the component 1 or the blade 3, as the
case may be.
Furthermore, it is advantageous if a length/diameter ratio of at
least one passage 7, 7' is greater than five. Furthermore, in order
to ensure a reliable closing off of the passage 7, 7' towards the
surface 6 of the component 1, a width of the cavity or the passage
7, 7', as the case may be, is less than 1 mm, preferably in the
region of about 0.2 mm. In this case, different cross sectional
shapes of the passages 7 and 7' are shown according to FIG. 3,
wherein the passage 7 tapers in its width towards the surface 6 of
the component, while the passage 7' has a constant width.
A directly bridged passage 7 is shown in FIG. 4, wherein the
coating 9 in the region of the passage 7 has a pillar-like
construction of fine dendrites. The orientation of the dendrites in
this case is parallel to the orientation of the substrate of the
basic body 8 and at the same time epitaxially hardens with the
substrate. This is especially advantageous when the component 1 or
the blade 3, as the case may be, is subjected to a cyclic thermal
and mechanical stress, as this is the case, for example, in gas
turbines. In FIG. 4 it is exemplarily indicated that the side edges
of the passage 7 which are oriented towards the coating 9 can melt
off or melt down, as the case may be, when applying the coating 9
and can then deviate considerably from the original shape, which is
shown by a discontinuously drawn line.
According to FIG. 5, a passage 7 which is produced according to the
same method is shown, wherein in this case the structure was
modified in an advantageous way, for example by laser melting,
after applying the coating 9. Furthermore, the basic body 8 is able
to have been preheated, especially by a laser, before the metal
forming. As a preheating temperature, for example 1100.degree. C.
comes into consideration, as a result of which high temperature
gradients inside the interaction zone, and therefore inside a
connecting zone between coating 9 and basic body 8, can be reduced.
At the same time, the higher ductility of the base material, as
result of heating it, and also the lower temperature gradients,
contribute to a reduction of a risk of cracks during hardening of
the coating 9.
A method for producing at least one passage 7, which is embedded in
an outer wall 5 of a component 1 of a turbomachine by coating the
outer surface 6, is to be briefly described in the following.
In a first method step, a passage-like cavity, called a passage 7,
7', is first introduced in the basic body 8 of the component 1.
This can be carried out, for example, mechanically and/or
electrochemically and/or photochemically and/or by a laser,
especially by a short pulse laser.
After that, a local surface melting of the basic body 8, at least
on the two sides of the passage 7, 7', is carried out, wherein
again a laser is also used in this case for melting the basic body
8.
The application and melting of a coating 9, at least in the region
of the passage 7, 7', is carried out in one working cycle with the
melting of the basic body 8, wherein the coating 9, the process
temperature, and the width of the passage 7, 7' are matched to each
other so that the molten coating material, owing to its surface
tension, does not penetrate into the passage 7, 7'. Therefore, no
filling material is required for closing off the passage 7, 7', as
this is the case in the production processes according to the prior
art. Rather, for example, a metal powder is used, which in the
molten state forms a bridge across the passage 7, 7' on account of
its surface tension and, as a result, closes this off towards the
surface 6 of the component 1. It is important for a preferred
embodiment that the material properties of the coating powder are
tailored to the respective coating process, so that the creation of
a monocrystal structure is benefited. The application of the
coating 9 to the basic body 8 can be carried out, for example, by
plasma spraying and/or by an electron beam evaporation process
and/or by a laser. A LMF method (laser metal forming), especially
an E-LMF method (epitaxial LMF), will be preferable for producing
an epitaxial coating, and therefore a monocrystalline coating 9, on
the basic body 8 which is preferably also monocrystalline.
Finally, a controlled cooling and hardening of the molten coating
material can be carried out in such a way that a metallurgical
connection to the basic body 8 on the two sides of the passage 7,
7' is achieved, and the passage 7, 7' is bridged towards the
surface 6 by the hardening coating material. After that, the
surface 6 can subsequently be processed and/or smoothed by a laser,
as a result of which a modified surface 6 can be achieved. This
"modification" is preferably the creation of a monocrystalline
structure inside the coating 9.
The cross sectional shape and the dimensioning of the passage 7, 7'
in this case can be accurately controlled, as a result of which the
desired cross sectional shape of the passages 7, 7' can be
relatively accurately formed and the course of the passage 7, 7'
can also be largely accurately defined.
With an LMF method, the melting of the basic body 8 and the
application and also the melting of the coating material can be
carried out simultaneously, which simplifies the application of the
coating 9. The use of an E-LMF method, by suitable selection of the
method parameters, creates the possibility of allowing the coating
9 to harden in a monocrystalline manner, wherein at the same time
the possibility is presented to basically produce the same
crystallographic orientation for the coating 9 and for the basic
body 8. By this crystallographic orientation of the coating 9 and
the basic body 8, which is the same after cooling, the
thermophysical properties of the coating material can be the same
as those of the basic body 8, on account of the propagating
dendrite arms and the pillar-like growth, as a result of which the
service life can be increased.
As already indicated further above, the application of the coating
9 and the surface modification can be designed as a two-step
process, in which, in a first step, the coating 9 can be applied to
the basic body 8 by a suitable method (see above), and in which, in
a second step, the monocrystalline structure can be realized inside
the coating 9 by a suitable remelting method, for example by a
suitable laser.
By the arrangement or production of the cooling passages 7, 7'
according to principles of the present invention, as the case may
be, an effective cooling of the component 1 can be achieved, and,
therefore, the tolerable turbine inlet temperature can be increased
by 50K to 125K. Naturally, the passages 7, 7' which are produced
according to the invention can also be combined with other cooling
methods, like, for example, a transpiration cooling method.
According to FIG. 6, the coating 9 in another embodiment can also
be applied to the basic body 8 so that it extends across a
plurality of passages 7 or covers a section of the basic body 8
which includes a plurality of passages 7, as the case may be. It is
especially possible to provide the entire surface 6 of the
respective component 1, which is exposed to thermal stress, first
with the coating 9 and then with the thermal protection layer
10.
Furthermore, when applying the coating 9, attention can be paid to
a first phase of hardening of the coating material being of the
.gamma. type. By adjusting the method parameters, attention can be
additionally or alternatively paid to a so-called CET
(columnar-to-equiaxed-transition), therefore a transition from a
directed to a globulitic crystal structure, being avoided. For this
purpose, it is additionally or alternatively expedient to select
the method parameters and the coating material so that, as far as
possible, the formation of new crystallization germs when applying
the coating 9 is avoided. In this way, an epitaxial construction of
the coating 9 on the basic body 8 can especially be achieved.
It is basically possible that the monocrystal structure which is
preferred for the basic body 8 is altered as a result of applying
the coating 9. By an additional melting process, a reconstruction
of the monocrystal structure of the basic body 8 can be expediently
achieved. This additional melting process can be carried out, for
example, at the same time with the melting of the coating 9, in
order to transform in this a polycrystalline structure into a
monocrystal structure.
TABLE-US-00001 List of designations 1 Component 2 Region exposed to
hot gas 3 Blade 4 Blade root 5 Outer wall 6 Surface 7, 7'
Passage/cavity 8 Basic body 9 Coating 10 Temperature/thermal
protection layer 11 Connecting passage 12 Passage longitudinal
axis
While the invention has been described in detail with reference to
exemplary embodiments thereof, it will be apparent to one skilled
in the art that various changes can be made, and equivalents
employed, without departing from the scope of the invention. The
foregoing description of the preferred embodiments of the invention
has been presented for purposes of illustration and description. It
is not intended to be exhaustive or to limit the invention to the
precise form disclosed, and modifications and variations are
possible in light of the above teachings or may be acquired from
practice of the invention. The embodiments were chosen and
described in order to explain the principles of the invention and
its practical application to enable one skilled in the art to
utilize the invention in various embodiments as are suited to the
particular use contemplated. It is intended that the scope of the
invention be defined by the claims appended hereto, and their
equivalents. The entirety of each of the aforementioned documents
is incorporated by reference herein.
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